1. Field of the Invention
The present invention relates to a hydrophilic polyester fiber, a hydrophilic nonwoven fabric of the polyester fiber, and their production and more particularly relates to a polyester type fiber having durable hydrophilicity and possible of keeping the hydrophilicity even if being formed into a nonwoven fabric by entangling the fiber by, for example, a water jet entangling method, a hydrophilic nonwoven fabric of the polyester fiber, and their production method.
2. Description of the Related Art
Owing to relatively excellent properties, the polyester represented with poly (ethylene terephthalate) has been used in a wide range of fields for materials for clothes and domestic and industrial various materials as well. Especially, in the textile industry, owing to the excellent physical and chemical properties and economical properties, the polyester has widely been used as a raw material for woven fabrics and nonwoven fabrics.
However, the polyester type fiber is a hydrophobic fiber and has disadvantages that the fiber is easy to be electrically charged and that the fiber is not provided with hydrophilicity. In order to improve such disadvantages, a variety of methods have been proposed. That is, a method (disclosed in Japanese Patent Publication No. 63-12897(1988)) for obtaining a block copolymer by adding a specified phosphorus compound, a hydrophilic substance, at the period of polymerization of a polyester, a method (disclosed in Japanese Patent Application Laid-Open No. 59-211676(1984)) by adding a hydrophilic substance at the time of spinning, a method (disclosed in Japanese Patent Publication No. 57-386(1982)) by graft-polymerizing a hydrophilic substance with the surface of a fiber, a method (disclosed in Japanese Patent Application Laid-Open No. 59-47476(1984)) for treating fibers with low temperature plasma, a method (disclosed in Japanese Patent Application Laid-Open No. 62-19165(1987)) by sticking an aqueous dispersion of a polyester ether copolymer containing a hydrophilic group to the surface of a fiber, and the like.
However, the methods by adding hydrophilic substances or graft polymerization have defective points, for example, that the properties of a polyester fiber are sometimes deteriorated and that the productivity is sometimes worsened. Further, the method by sticking an aqueous dispersion of a polyester ether copolymer containing a hydrophilic group to the surface of a fiber, the durability of the hydrophilicity is insufficient. Therefore, the polyester ether copolymer on the fiber surface is parted from the surface and cannot keep the hydrophilicity by the entangling treatment with high pressure water jet or being immersed just like a hand towel in water or an aqueous solution for a long duration.
In case of a nonwoven fabric, although it is possible to produce a hydrophilic nonwoven fabric by mixing a hydrophilic fabric, for example, rayon and bleached cotton, such as method has disadvantages that a bulky nonwoven fabric can not be obtained, the productivity is low, the cost is high and the like.
The object of the present invention is to provide a hydrophilic polyester type fiber having highly durable hydrophilicity as compared with a fiber produced by a conventional method and possible of keeping the hydrophilicity even in case of entangling treatment with high pressure water jet and in case of being immersed in water or an aqueous solution for a long duration, to provide a nonwoven fabric using the fiber, and to provide economical methods for producing these fiber and fabric.
The characteristic constitution of the hydrophilic polyester fiber relevant to the present invention is that the fiber is made hydrophilic by supplying an aqueous mixed dispersion to the surface and then heating the resultant fiber to 35xc2x0 C. or higher: and the aqueous mixed dispersion contains a polyester-polyether block copolymer which is a copolymer of a polyester component and a polyether component and is stable at a temperature lower than 35xc2x0 C. but if the dispersion is heated to 35xc2x0 C. or higher, its dispersion state is broken to precipitate the polyester-polyether block copolymer.
With such a constitution, it is made possible to economically provide a hydrophilic polyester fiber having highly durable hydrophilicity as compared with a fiber produced by a conventional method and possible of keeping the hydrophilicity even in case of entangling treatment with high pressure water jet and in case of being immersed in water or an aqueous solution for a long duration.
The foregoing polyester-polyether block copolymer is preferably produced by copolymerization of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or an ester derivative of them as an acid component and polyoxyalkylene glycol or its derivative with 500 or higher number average molecular weight as a polyether component in 5 to 150 wt. % ratio to the polyester.
Further, the foregoing polyester-polyether block copolymer is preferably added in 0.05 to 2.0 parts by weight to 100 parts by weight of the fiber.
Further, the aqueous mixed dispersion contains an anionic surfactant and a cationic surfactant other than the polyester-polyether block copolymer and also a nonionic surfactant and/or an amphoteric surfactant, and is preferable to produce ion complexes when being heated and to break the dispersion state.
Further, the foregoing polyester fiber is preferably a polyester containing mainly ethylene terephthalate unit.
Further, the foregoing polyester fiber is preferably a fiber composed of two kinds of polyesters having melting points or softening points different from each other by at least 20xc2x0 C. and forming a core-sheathed type or side by side type conjugate.
The characteristics of the hydrophilic nonwoven fabric relevant to the present invention are that a fiber web containing 20 wt. % or more of a hydrophilic polyester fiber is entangled by at least one of the following entangling methods; a needle punching method, a stitch bonding method, a thermal bonding method, and a water jet entangling method; that the foregoing hydrophilic polyester fiber is made hydrophilic by applying an aqueous mixed dispersion to the surface and then heating the resultant fiber at 35xc2x0 C. or higher; and that the foregoing aqueous mixed dispersion contains a polyester-polyether block copolymer which is a copolymer of a polyester component and a polyether component and is stable at a temperature lower than 35xc2x0 C. but if being heated to 35xc2x0 C. or higher, its dispersion state is broken to precipitate the polyester-polyether block copolymer.
With such characteristics, it is made possible to economically provide a hydrophilic nonwoven fabric having highly durable hydrophilicity and possible of keeping the hydrophilicity even in case of entangling treatment with high pressure water jet and in case of being immersed in water or an aqueous solution for a long duration.
Further, the foregoing hydrophilic nonwoven fabric preferably has basis weight of 20 to 2000 g/m2 and the water absorption 3 minutes after measurement by Larose method of 30 wt. % on the basis of the nonwoven fabric weight.
Further, in the foregoing hydrophilic nonwoven fabric, it is preferable that the foregoing polyester-polyether block copolymer is deposited on the surface of a long fiber having a fiber diameter of 0.5 to 40 xcexcm and of which 80 wt. % or more is the foregoing polyester component.
Further, in the foregoing hydrophilic nonwoven fabric, the foregoing polyester-polyether block copolymer is preferably composed of an aromatic dicarboxylic acid and/or an aliphatic dicarboxylic acid as an acid component and polyoxyalkylene glycol or its derivative with 500 or higher number average molecular weight as a polyoxyalkylene glycol component and the copolymerization ratio of the foregoing polyoxyalkylene glycol component is in 5 to 150 wt. % ratio to the total polymer weight.
Further, in the foregoing hydrophilic nonwoven fabric, the foregoing polyester-polyether block copolymer is preferably added in 0.05 parts by weight or higher to 100 parts by weight of the nonwoven fabric.
Further, in the foregoing hydrophilic nonwoven fabric, the foregoing mixed dispersion is preferable to further contain an anionic surfactant and a cationic surfactant and also a nonionic surfactant and/or an amphoteric surfactant and is preferable to produce ion complexes when being heated and to break the dispersion state.
Further, the foregoing hydrophilic nonwoven fabric preferably has basis weight of 100 to 2000 g/m2 and made of a long fiber made durably hydrophilic for civil engineering by a needle punching process.
Further, the foregoing hydrophilic nonwoven fabric preferably has basis weight of 30 to 300 g/m2 and made of a long fiber made durably hydrophilic for civil a filter by being integrated by thermal fusion.
The method for producing a hydrophilic polyester fiber relevant to the present invention has the following characteristic: the method is for providing hydrophilicity by supplying an aqueous mixed dispersion to the surface and heating at 35xc2x0 C. or higher and the aqueous mixed dispersion contains a polyester-polyether block copolymer, which is a copolymer of a polyester component and a polyether component, is stable at a temperature lower than 35xc2x0 C. but if being heated to 35xc2x0 C. or higher, its dispersion state is broken to precipitate the polyester-polyether block copolymer.
Further, in the foregoing method for producing a hydrophilic polyester fiber, the foregoing polyester-polyether block copolymer is preferably produced by copolymerization of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or an ester derivative of them as an acid component and polyoxyalkylene glycol or its derivative with 500 or higher number average molecular weight as a polyether component in 5 to 150 wt. % ratio to the polyester.
The method for producing a hydrophilic polyester type nonwoven fabric relevant to the present invention has the following characteristic: the method comprises steps of supplying an aqueous mixed dispersion, which is stable at a temperature lower than 35xc2x0 C. but if being heated to 35xc2x0 C. or higher, its dispersion state is broken to precipitate the polyester-polyether block copolymer, to a nonwoven fabric containing at least 80 wt. % of a polyester fiber and heating at 35xc2x0 C. or higher.
By such a constitution, it is made possible to economically provide a method for producing a hydrophilic polyester type nonwoven fabric having highly durable hydrophilicity and possible of keeping the hydrophilicity even in case of entangling treatment with high pressure water jet and in case of being immersed in water or an aqueous solution for a long duration.
Further, in the foregoing method for producing a hydrophilic polyester type nonwoven fabric, the polyester-polyether block copolymer is preferably produced by copolymerization of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or an ester derivative of them as an acid component and polyoxyalkylene glycol or its derivative with 500 or higher average molecular weight as a polyether component in 5 to 150 wt. % ratio to the polyester.
Further, in the foregoing method for producing a hydrophilic polyester type nonwoven fabric, 0.05 parts by weight or more of the polyester-polyether block copolymer is preferably added to 100 parts by weight of the nonwoven fabric.
Further, in the foregoing method for producing a hydrophilic polyester type nonwoven fabric, the foregoing aqueous mixed dispersion contains an anionic surfactant and a cationic surfactant other than the polyester-polyether block copolymer and also a nonionic surfactant and/or an amphoteric surfactant, and is preferable to produce ion complexes when being heated and to break the dispersion state.
Further, in the foregoing method for producing a hydrophilic polyester type nonwoven fabric, the foregoing nonwoven fabric containing at least 80 wt. % of the polyester fiber is produced by entangling a fiber by a water jet entangling method.
Further, in the foregoing method for producing a hydrophilic polyester type nonwoven fabric, the foregoing nonwoven fabric containing at least 80 wt. % of the polyester fiber is produced by spunbonding.